With the continuous development of science and technology, more and more high-tech information technology is widely used in various industries and fields, and power plants are no exception. At present, China's power plants have widely used DCS in thermal control systems. This system can not only effectively improve the operational safety of power plant units, but also greatly improve operational efficiency, making the thermal control system gradually transition to automation and intelligence, and it can also be effective. It saves production costs, improves the social and economic benefits of enterprises, and plays an important role in the survival and development of thermal power plants, thereby promoting the development of China's economy.
The industrial site has a wide range of power consumption and a large influence area. Therefore, the quality of the power supply must be ensured. If the industrial site is seriously disturbed, the entire automation control system will also be seriously damaged. Therefore, the design of the power supply system will have a direct impact on the safety of the control system. The design of the DCS control system will be affected by the following factors: the anti-interference of the power supply system; the power supply of the DCS should not be affected by the loss of power from the external equipment; the control system requires that the power supply in the power-off occasion is not repeatedly configured.
DCS upper control system power supplyDCS upper control system includes human interface equipment, field control station and communication
The three core parts of the network system are independent of their power supply. They are strictly differentiated from the power supply of the indoor lighting system and the power supply for construction and maintenance. It requires a continuous, stable and safe power supply.
Single loop power supply
Single-loop power supply is only one power supply, or UPS power supply, or EVS power supply. They all have a disadvantage that when the system fails, the whole system will stop running. The advantage is that the investment cost is small.
Single UPS power supply
UPS is abbreviated as uninterruptible power supply. It is a power protection device that contains energy storage devices and uses inverter as the main component to stabilize the output of the voltage. Mainly composed of rectifiers, batteries, inverters, etc., they complete AC to DC, DC and then AC, and battery charging and discharging process.
Single-channel UPS power supply, generally 380VAC sent from the electrical high-voltage cabinet directly into the UPS host, after the UPS rectification, inverter, battery charge and discharge, and then by
The UPS outputs 220VAC to the load. Figure 1 shows a simplified diagram of a single UPS supply.
In a single UPS power supply, under normal circumstances, the electric power is charged by the UPS main unit. When the electric power is de-energized for some reason, the entire DCS will not immediately slam, and the UPS reserve battery will immediately discharge to the load. Supplying two hours of electricity, the operator has enough time to deal with the emergency within two hours. At this time, the stability and reliability of the UPS determine the stability of the entire DCS. Therefore, the UPS must be regularly maintained to check whether the input and output of the host is normal, and whether the battery is charged and discharged normally. For the UPS main unit, check whether the input, output and output voltages are normal with a multimeter. Since the UPS battery pack is usually connected in series by multiple batteries, when one of the battery packs fails, the entire battery pack will not work normally. The DC bulbs are inspected one by one, in order not to affect the operation of the system, generally during the process of production and shutdown. The disadvantage of single-channel UPS power supply is that when the power is suddenly turned off, the battery can only supply power for a certain period of time, and it must be guaranteed at this time.
The UPS battery is normal, otherwise the entire DCS control system will be paralyzed, and a relatively reliable UPS is relatively expensive and the maintenance cost is high. Due to the energy storage function and relative reliability of the UPS, the single-channel UPS can be used as the power supply for the general DCS control system, or it can be used as the main circuit of the DCS control system with higher requirements.
Single-channel EVS power supply
EVS is abbreviated as regulated power supply. Single-channel EVS power supply is the 380VAC three-phase electric power sent by electric. After EVS, it is directly output to the load. Generally, EVS has an isolation transformer to ensure stable output of 220VAC AC. Figure 2 shows a single-channel EVS power supply diagram.
In the single-channel EVS power supply, since it does not have the energy storage function, when the electric power trips, the entire power supply system will be powered down, and when the electrical voltage fluctuates greatly, the output of the EVS will fluctuate, and even the EVS will be damaged, resulting in an interruption of the output. The entire control system will be paralyzed. Compared with other power supply equipment, a set of EVS is more economical and has a lower maintenance cost. Generally, single-channel EVS power supply is only used for power supply of small PLC control systems, and it is acceptable for production to accept failures. In the DCS control system, EVS is generally used to make the secondary circuit of the dual-loop power supply, and the EVS with reliable performance and good voltage regulation effect is selected.
Dual loop power supply
In order to overcome the shortcomings of single-loop power supply, dual-loop power supply can be used, that is, a DCS control system uses two loop power supply systems to supply power, or a redundant system, or a redundant system, depending on the power switching device.
UPS, EVS dual circuit switching power supply
Because the single-channel UPS has energy storage function and high reliability, it can be used for main loop power supply of high DCS control system. In order to facilitate regular maintenance, EVS, which is more economical than UPS, is used as a secondary circuit. As shown in Figure 3, two ways
The power supply is separately output to a power switching device, and the output of the power switching device is supplied to the load. When the main circuit UPS output fails, the secondary circuit outputs the supply load, thus avoiding the power failure caused by the battery failure due to the main circuit trip; at this time, it must be ensured that the secondary circuit EVS power supply is normal, and the power switching device is also critical. For the power switching device, it is generally redundant, that is, the main circuit is the power supply output. When the main circuit output is powered down, the secondary circuit output is switched immediately. However, in the process of switching, it is inevitable that there is a time difference. This time difference is very important. The above is in milliseconds. There are different requirements for different DCS to withstand the time difference. Therefore, each manufacturer will develop its own power switching device, and some even claim to be able to seamlessly switch, absolutely guaranteeing the system's absence. Unexpected power supply; for ordinary power switching devices are realized by the principle of relay action, the relay normally open and closed electric shock action is absolutely time difference, if the load of the power supply can withstand this time difference, you can use ordinary switching Device, but for power plant and other control systems, where safety, reliability, stability and other aspects are required to be relatively high, it is necessary to use a highly reliable power switching device.
In summary, the UPS and EVS dual-loop switching power supply can avoid the disadvantage of single-channel power supply, but the power switching device in the dual-loop power supply is relatively high, and the power switching device determines the safety of the entire DCS.
Using USB drives already saves paper, but when you choose a custom wood USB key, you can help offset your impact on the environment even further. Organic materials are back in demand. You can now reap the benefits in your promotional USB project by including a pure & natural image to your brand.
This stylish wooden custom flash drive has a magnet on the inside of the cap to keep it firmly in place while not in use. With the use of trendy craftsmanship, this wooden usb key add natural richness to your branding. This wooden USB stick works great for trade industries, health spas, photographers and other hospitality businesses. Our Konchang wooden USB drives are popular with photographers & allow you to showcase your promotional materials, photos, or videos.
Specifications
These wood USB keys offer all of the benefits of a traditional USB Flash Drive, but with more flair and practical applications. This rectangular wooden USB stick is created from a real piece of wood. It can easily be used to store your promotional marketing material, photos, videos or documents. The wooden USB key can be customized with your logo laser engraved or imprinted on 1 or 2 sides.
Our wood usb drive can also be imprinted, engraved or customized with a special [burn" process for a truly natural look. You may personalize the exterior finishing of the Natural wood tones in either Walnut, Mahogany, Bamboo, or Maple.
Konchang offers up to 600MB of FREE data loading so you can avoid the inconvenience and save time of doing it yourself. As with any USB Drive, we also offer a complimentary virtual proof to make your purchase decision easier.
Wooden Card Pen Drive,Wooden Usb Flash Pen Drive,Wood Usb Flash Drive Bulk,Wood Usb Flash Drive With Box,usb flash drive for photography
Shenzhen Konchang Electronic Technology Co.,Ltd , https://www.konchangs.com